Sudan's de facto ruler, army chief Abdel Fattah al-Burhan, said Saturday his government would not join peace talks with rival paramilitaries in Switzerland, vowing instead to "fight for 100 years".

"We will not go to Geneva... we will fight for 100 years," Burhan, whose troops have been battling the paramilitary Rapid Support Forces (RSF) for over 16 months, told reporters in Port Sudan.

The United States opened talks in Switzerland on August 14 aimed at easing the human suffering and achieving a lasting ceasefire.

While an RSF delegation showed up, the Sudanese armed forces were unhappy with the format and did not attend, though they were in telephone contact with the mediators.

The talks were co-hosted by Saudi Arabia and Switzerland, with the African Union, Egypt, the United Arab Emirates and the United Nations completing the so-called Aligned for Advancing Lifesaving and Peace in Sudan Group (ALPS).

They wrapped up on Friday without a ceasefire but with progress on securing aid access on two key routes into the country, which is gripped by one of the world's worst humanitarian crises.

The brutal conflict has forced one in five people to flee their homes, while tens of thousands have died. More than 25 million across Sudan -- more than half its population -- face acute hunger.